Women, and even men, currently have a tendency to wish to look youthful for as long as possible and consequently seek to fade out the age marks on the skin, which are reflected in particular by wrinkles and fine lines. In this respect, the media and the fashion world report about products intended to keep the skin radiant and wrinkle-free for as long as possible, which are signs of youthful skin, and all the more so since the physical appearance acts on the psyche and/or on the morale.
Hitherto, wrinkles and fine lines were treated using cosmetic products containing active agents acting on the skin, for example by moisturizing it or by improving its cell renewal or alternatively by promoting the synthesis of collagen, of which skin tissue is composed.
Although these treatments make it possible to act on the wrinkles and fine lines caused by chronological or intrinsic ageing, and also on those caused by photoageing, they have no effect on expression wrinkles and fine lines.
Hitherto, the only means commonly used for acting on expression wrinkles is botulinum toxin, which is especially injected into the wrinkles of the glabella, i.e. the wrinkles between the eyebrows (see J. D. Carruters et al., J. Dermatol. Surg. Oncol., 1992, 18, pp. 17-21).
Various compounds have been proposed that are capable of affording a muscle-relaxant effect when they are applied topically to the skin, thus making it possible to act on expression wrinkles via another route. Among these compounds that may especially be mentioned are antagonists of the receptors associated with the calcium channels (FR-2 793 681), and in particular manganese and its salts (FR-2 809 005) and alverine (FR-2 798 590); and agonists of the receptors associated with the chlorine channels, including glycine (EP-0 704 210) and certain extracts of Iris pallida (FR-2 746 641).
However, there is still a need for compounds of natural origin that are effective in smoothing out or fading out expression wrinkles and fine lines.